"Bud Light is starting this fight for one simple reason. They are scared," MillerCoors CEO Gavin Hattersley said in a note to distributors on Sunday, as quoted in Behind Beer, a blog owned by the beer giant.

Miller Lite ran a full page ad in the New York Times, slamming the "unnecessary #corntroversy." Bud Light even ended up backing away from its apparent anti-corn stance following backlash from the corn lobby.

"In the Bud Light Kingdom we love corn too!" the brand tweeted.

Why are Bud Light, Miller Lite, and Coors Light throwing down in this corn-syrup-drenched battle? First, all three brands are struggling to win over drinkers. And second, they seem to think that being seen as the higher quality or most nutritious option could be key to survival.

The sales slump comes as the wider beer industry struggles to appeal to millennials and Gen Z in the same way it did to prior generations.

However, Coors Light, Miller Lite, and Bud Light are among a segment that is being hit particularly hard: domestic premium brands. While this category, which also includes Budweiser, includes most of the best-selling beers in the US, overall sales dropped by 4.2% in 2018.

"The Premium and Premium Light segments remain under pressure as consumers trade up to higher-priced tiers," Anheuser-Busch InBev CEO Carlos Brito said in a call with investors in October.

To reverse the downward trend, these beers are looking towards the bright spots in the beer industry and trying to take notes. Craft beer and domestic super premiums (like Michelob Ultra and Budweiser Reserve) were among the categories that grew in 2018. These are brands that are both more expensive and perceived as higher-quality products.

So, to better compete with these pricier brews, Coors Light, Miller Lite, and Bud Light are on a mission to convince customers that they are the higher-quality light beer, whether that means a lack of corn syrup or simply fewer calories. As the battle continues, you can expect these iconic light beers to keep trying to class up their acts.